 import java.util.Scanner;
 import java.text.DecimalFormat;

 public class PP37
 {
    public static void main(String[] args)
    {
      double a, b, c, s, area;
      
      Scanner scan = new Scanner(System.in);
  
      System.out.print("Enter the length of side a: ");
      a = scan.nextDouble();

      System.out.print("Enter the length of side b: ");
      b = scan.nextDouble();

      System.out.print("Enter the length of side c: ");
      c = scan.nextDouble();

      s = (0.5)*(a + b + c);
      area = Math.sqrt(s*(s-a)*(s-b)*(s-c));

      DecimalFormat fmt = new DecimalFormat("0.###");

      System.out.println("The area of this triangle: " +fmt.format(area));
    }
 }

